M35A2 Brake Problems. New owner

[captkyle]

Well I finally bit the bullet and got my very own M35A2. 1970, multi-fuel, already on 46"s. I am going threw it trying to fix problems before they start, ie bearings, fluids, and such. The brakes never worked well at all. As I troubleshoot, I realized that the booster is not boosting. Please excuse my ignorance, but I am used to dealing with car brakes, and full air brakes, this air over hydro is foreign to me. So, I got air coming from the tank into the driverside of the booster in to what looks to be a diaphragm, but no air is coming out, I am assuming that this is where when the brake petal is depressed that it releases air into the booster, is that correct? Either way, when the brake petal depresses, still no air is released. Basially, I got air coming into the booster, but no air actually 'boosting'. Any ideas? And from what I can tell, a hydraulic line comes from the master cylinder into the booster, and I would believe that that fluid is what actually activates the booster. Is that correct? I have read through some fourums on this site for a while now. It is a very well run place, with alot of great info. Thanks in advance!

 

[GHall]

I believe you're talking about the airpac, you can either buy a new one or rebuild it. Do a google search "deuce airpac rebuild" or something to the effect, you will get plenty of info I'm sure. Make sure that's the part that's bad before you go taking it apart. There are plenty of vendors that sell NOS, rebuilt or new parts also.

 

[Woodsplinter]

Welcome to the club- nice deuce!

I don't know enough about the brake system to answer your question but that topic has been covered in depth on this site. Searching the site for what you want is sometimes frustrating- Google can help a lot.

 

[welldigger]

Your air pac is shot. Very common problem. Pull the large air end off and if there is too much pitting to hone out easily don't bother attempting to rebuild it. Just get a new one. Also pull the rubber boot back on your master cylinder. If its dry your good. If its got brake fluid back behind the boot you need to rebuild/replace your master cylinder.

 

[captkyle]

Ok. That makes sence. Next question, is an air pac off a 90 m35A3 interchangeable with mine??

 

[welldigger]

Yes. A3s have dual air packs. Both are identical. They should be the "short" style. They interchange with the older "long" style. Beware of used air packs though. Its common for them to be bad also.

 

[captkyle]

Great, thanks for the info!

 

[welldigger]

NP. Pm me if you need any more assistance.

 

[gimpyrobb]

Your air pac is shot. Very common problem. Pull the large air end off and if there is too much pitting to hone out easily don't bother attempting to rebuild it. Just get a new one. Also pull the rubber boot back on your master cylinder. If its dry your good. If its got brake fluid back behind the boot you need to rebuild/replace your master cylinder.

Might want to add,
be careful, that can has a fairly powerful spring in there.

 

[welldigger]

I don't know about the long style but in the short style the spring is captured on the piston. You can pull the housing off with minimal risk. Is the spring not captured on the long style?

 

[gimpyrobb]

No, its not.

 

[welldigger]

Thanks for clarifying that gimp. I have never had a long one apart.

 

[rlwm211]

The air piston on the airpack and the cylinder housing is aluminum and usually is not pitted in any way. The slave bore can get rusty and this is one of two areas where you have to be sure that they are smooth.

The rebuild process for the old style airpack (longer air piston with a cap on the end where the air line connects to the cover) is not that difficult and is well described in
TM 9-2320-209-34-2-1 page 509 (12-7). A rebuild kit will run from 25 to 50 depending on where you get one.

I would strongly recommend not removing any seals or gaskets as they tell you to in the instructions. Leave them in place on all the pieces you take apart. Only exchange the seals and such while you are reassembling the airpack. This way you do not run the risk of reversing a seal which would cause a problem.

It is a good idea to rebuild the master cylinder at the same time. You can get a new one reasonably if you want to avoid this chore. The same manual has the instructions for doing this but pretty much it is self evident as to how to take it apart and rebuild it.

I would also pull each hub and inspect the wheel cylinders looking for seepage behind the dust boot on each end . If you see brake fluid rebuild or replace the wheel cylinder.

Packing the wheel bearings is a part of this process and you also will make a primary and secondary adjustment on the brake shoes as a part of reassembly.

This is not difficult work but it is heavy work. You will need a lug wrench or sockets. A bearing nut socket is a handy tool to have should be in your tool kit.

If you plan on keeping the deuce long term I would invest in a gear wrench for removing the lug nuts and inners. This makes short work of taking off tight lug nuts without spinning the inner at the same time. Just a suggestion.

I am quite sure if you were to search this site for "airpack rebuild" or "Brake service" you would find a hundred good threads with write ups that would spell out the work required.

I hope this is helpful and of course, I am always listening if anyone has a suggestion as to how to do things easier.

 

[peashooter]

Yes. A3s have dual air packs. Both are identical. They should be the "short" style. They interchange with the older "long" style. Beware of used air packs though. Its common for them to be bad also.

The "short" style air packs should only be used on the dual circuit brake trucks. They are short because they dont need as much travel to activate half the brakes. The "Long" style air pack can be used on both the single and dual circuit trucks because it has enough travel to move enough fluid to activate all the wheel cylinders. If you use a short style air pack on a single circuit deuce, it will be possible to run out of Airpack stroke before your brakes are engaged enough..... especially if your shoes arent adjusted close.

 

[DESERTRATINAZ]

THANK YOU THANK YOU rlwm211

THANK YOU rlwm211

The air piston on the airpack and the cylinder housing is aluminum and usually is not pitted in any way. The slave bore can get rusty and this is one of two areas where you have to be sure that they are smooth.

The rebuild process for the old style airpack (longer air piston with a cap on the end where the air line connects to the cover) is not that difficult and is well described in
TM 9-2320-209-34-2-1 page 509 (12-7). A rebuild kit will run from 25 to 50 depending on where you get one.

I would strongly recommend not removing any seals or gaskets as they tell you to in the instructions. Leave them in place on all the pieces you take apart. Only exchange the seals and such while you are reassembling the airpack. This way you do not run the risk of reversing a seal which would cause a problem.

It is a good idea to rebuild the master cylinder at the same time. You can get a new one reasonably if you want to avoid this chore. The same manual has the instructions for doing this but pretty much it is self evident as to how to take it apart and rebuild it.

I would also pull each hub and inspect the wheel cylinders looking for seepage behind the dust boot on each end . If you see brake fluid rebuild or replace the wheel cylinder.

Packing the wheel bearings is a part of this process and you also will make a primary and secondary adjustment on the brake shoes as a part of reassembly.

This is not difficult work but it is heavy work. You will need a lug wrench or sockets. A bearing nut socket is a handy tool to have should be in your tool kit.

If you plan on keeping the deuce long term I would invest in a gear wrench for removing the lug nuts and inners. This makes short work of taking off tight lug nuts without spinning the inner at the same time. Just a suggestion.

I am quite sure if you were to search this site for "airpack rebuild" or "Brake service" you would find a hundred good threads with write ups that would spell out the work required.

I hope this is helpful and of course, I am always listening if anyone has a suggestion as to how to do things easier.